1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copying machine, a printer, a recorded image display device, and a facsimile, forming a visible image by an electrophotographic system.
2. Description of Related Art
For example, in recent years, as a multiple function processing machine and a facsimile having a copy and printer function, an image forming apparatus of an electrophotographic system has been widely used. Then, the image forming apparatus of an electrophotographic system has been required to be faster, reduce the cost, and improve user operability.
In the image forming apparatus which forms an image on a horizontally conveyed sheet, a configuration which transfers the image onto the lower surface of the sheet in a vertical direction is used. In the case of one-side image formation, the sheet is discharged with its transfer side facing downward from the image forming apparatus without being reversed. The image forming apparatus discharges the sheet in the page order without reversing the sheet. Accordingly, the reversing time of the sheet can be unnecessary so that the image forming apparatus can be faster.
In such a configuration, a sheet conveying path from a transfer portion via a fixing device to a discharge portion is arranged above an image forming portion. Due to this, the sheet onto which an unfixed image is transferred by the transfer portion is conveyed to the fixing device by absorbing the upper surface of the sheet in a vertical direction.
The image forming apparatus will be generally described. In FIG. 6, reference numeral 1 denotes an apparatus body and process units 4a to 4d which individually form primary images of yellow, magenta, cyan, and black colors are arranged in the apparatus body 1.
An original to be image formed is read by an original reading device 2 so as to be converted to image data and is then output from each of laser scanners 3 for the respective colors. Reference numeral 9 denotes an intermediate transfer belt and a toner image primarily transferred onto the intermediate transfer belt 9 is transferred onto a sheet by a secondary transfer roller 10.
The sheet is conveyed via a longitudinal conveying path 13 to a pair of registration rollers 14. The pair of registration rollers 14 adjust the timing of sheet conveyance relative to skew feeding correction of the sheet and image writing.
On the downstream side of the image forming portion, there are provided a fixing device 16 which fixes the toner image onto the sheet as a permanent image and a pre-fixing conveying portion 31 which absorbs and conveys the sheet to the fixing device 16. Upper and lower guide portions forming the conveying path are provided. Either of the guide portions is separated. When the jam recovery operation of the apparatus body 1 is performed, the user separates the guide portion to remove the sheet.
For example, when there is a jammed sheet near the pre-fixing conveying portion 31, the pre-fixing conveying portion 31 is opened in an arrow C direction to perform the jam recovery operation in a space formed thereby (see Japanese Patent Application Laid-Open No. 5-193790).
To achieve the high productivity of the image forming apparatus, the jam recovery need be performed immediately. As illustrated in FIG. 7, an upper portion D including the original reading device 2 and the pre-fixing conveying portion 31 is provided in the apparatus body 1 so as to be opened and closed. The jam recovery operation of a sheet P on the conveying path from the pre-fixing conveying portion 31 to the fixing device 16 is performed in a space formed when the upper portion D is opened (see Japanese Patent Application Laid-Open No. 8-272229).
In JP-A No. 5-193790, the pre-fixing conveying portion 31 is opened and closed to secure the jam recovery space. However, the pre-fixing conveying portion 31 is provided in the apparatus body 1. Due to this, the amount of opening and closing the pre-fixing conveying portion 31 cannot be sufficiently secured. Accordingly, the jam recovery cannot be easily performed.
In JP-A No. 8-272229, to support the opened and closed upper portion D, high rigidity and high accuracy are required for the apparatus body 1. The cost of components and assembling can be increased.